Re: [PATCH] media: i2c: adv7343: fix the DT binding properties

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Monday 23 September 2013 15:33:10 Stephen Warren wrote:
> On 09/23/2013 05:50 AM, Laurent Pinchart wrote:
> > On Monday 23 September 2013 08:18:52 Prabhakar Lad wrote:
> >> On Fri, Sep 20, 2013 at 3:22 PM, Sylwester Nawrocki wrote:
> >>> On 09/20/2013 10:11 AM, Prabhakar Lad wrote:
> >>>> OK I will, just send out a fix up patch which fixes the mismatch
> >>>> between
> >>>> names for the rc-cycle, and later send out a patch which removes the
> >>>> platform data usage for next release with proper DT bindings.
> >>> 
> >>> I think the binding need to be fully corrected now, I just meant to not
> >>> touch the board file, i.e. leave non-dt support unchanged.
> >> 
> >> Ok
> >> 
> >>>> I'm OK with making regulator properties as optional, But still it would
> >>>> change the meaning of what DT is, we know that the VDD/VDD_IO .. etc
> >>>> pins are required properties (but still making them as optional) :-(
> >>>> 
> >>>> I think there might several devices where this situation may arise so
> >>>> just thinking of a alternative solution.
> >>>> 
> >>>> say we have property 'software-regulator' which takes true/false(0/1)
> >>>> If set to true we make the regulators as required property or else we
> >>>> assume it is handled and ignore it ?
> >>> 
> >>> I don't think this is a good idea. You would have to add a similar
> >>> platform data flag for non-dt, it doesn't sound right. I can see two
> >>> options here:
> >>> 
> >>> 1. Make the regulator properties mandatory and, e.g. define a fixed
> >>> 
> >>>    voltage GPIO regulator in DT with an empty 'gpio' property. Then
> >>>    pass a phandle to that regulator in the adv7343 *-supply properties.
> >>>    For non-dt similarly a fixed voltage regulator(s) and voltage
> >>>    supplies  would need to be defined in the board files.
> >>> 
> >>> 2. Make the properties optional and use (devm_)regulator_get_optional()
> >>> 
> >>>    calls in the driver (a recently added function). I must admit I don't
> >>>    fully understand description of this function, it currently looks
> >>>    pretty much same as (devm_)regulator_get(). Thus the driver would
> >>>    need to be handling regulator supplies only when non ERR_PTR() is
> >>>    returned from regulator_get_optional() and otherwise assume a non
> >>>    critical error. There is already quite a few example occurrences of
> >>>    regulator_get_optional() usage.
> >> 
> >> Thanks for pointing it I'll choose option 2 and post the patch.
> > 
> > Isn't regulator_get_optional() intended for devices that can have supplies
> > unconnected in normal use ?
> 
> I believe so, yes.
> 
> > The ADV7343 supplies are mandatory from a hardware
> > point of view, so I think we should use regulator_get(). Otherwise the
> > driver won't be able to tell the difference between a regulator that
> > isn't present yet (for instance because the regulator device/driver
> > hasn't been probed yet), which should result in deferred probing, and an
> > always-on regulator that has been left out.
> 
> So I think you want to make the supply properties mandatory in DT (since
> some form of supply is mandatory in HW), yet make the driver support
> broken DTs which don't have those properties, by error-checking the
> return value from regulator_get(). You might want to put a note into DT
> saying that a previous version of the binding didn't require those
> supply properties, so they may be missing from older DTs.

Are there such devices in the wild ?

-- 
Regards,

Laurent Pinchart